The value of flexible flight-to-route assignments in pre-tactical air traffic management

In European air traffic management, there are discussions regarding the future role of the network manager (NM): in particular, should the NM be able to assign flights to specific trajectories, should airspace users be allowed to freely choose their preferred trajectory, or something in between? In this paper, we develop a modeling framework that can be adapted to these settings to assess their effect on key performance indicators. We focus on the pre-tactical stage of planning air traffic for a future departure day, meaning that airspace capacity budgets are given and incoming flight intentions need to be offered one or several 'trajectory products' for a (possibly dynamically determined) charge. These trajectory products differ in the amount of flexibility that they provide the NM to route the flight. Charges are set so as to reward greater flexibility of airspace users with lower charges. The airspace user chooses one of the offered trajectory products according to a choice model that reflects their preferences given, among others, the product charges. Shortly before the departure day, the NM decides simultaneously on the routing (within the limits defined by the purchased trajectory products) and on each airspace's sector opening scheme (within the limits of the fixed capacity budgets) so as to minimize the overall displacement cost. Methodologically, the problem deviates from typical dynamic pricing problems in various major ways, e.g., featuring a boundary condition that we show to be NP-hard as well as fairness and revenue neutrality constraints. The problem is cast in the form of a dynamic program. We exploit a certain structure in the boundary condition to formulate an efficient heuristic. Based on a numerical case study, we find that the use of dynamically priced trajectory products achieves a cost performance close to the one obtained if the NM has a mandate to simply assign flights to trajectories. Therefore, this seems an attractive design for the role of the NM, giving airspace users some choice whilst achieving low overall costs.